A head-up display device in the related art displays a virtual image by projecting light representing an image onto a windshield of a vehicle and forming the image at an image forming position ahead of the windshield.
A position of an eyepoint (hereinafter, referred to as the eyepoint position) of an occupant varies with a physical size of the occupant. In order to use a head-up display device appropriately, it is necessary to adjust a position where light from the head-up display device goes incident on the windshield (hereinafter, referred to as the incident position) according to the eyepoint position.
The head-up display device described in Patent Literature 1 includes a concave mirror reflecting light to the windshield, and adjusts the incident position by rotating the concave mirror.